Brush holder with commutator brushes for electric motor



May 31, 1966 H. H. PFEIFER BRUSH HOLDER WITH COMMUTATOR BRUSHES FORELECTRIC MOTOR Filed April 4, 1963 F/6I4 F/6.5

F/G. 2. I

JNVf/V TOR HERMANN HELMUT PFEIFER ATTORNEY.

United States Patent BRUSH HOLDER WITH CUMMUTATOR BRUSHES FOR ELECTRICMOTOR Hermann Helmut Pfeifer, Pellergasse 38, Fischbach, near Nurnberg,Germany Filed Apr. 4, 1963, Ser. No. 270,645 Claims priority,application Germany, Apr. 7, 1962, W 28,116 3 Claims. (Cl. 310-244) Thepresent invention relates to a brush holder with commutator brushes foran electric motor, especially for one of a very small size, in which thebrushes are provided with leaf springs under initial tension forpressing the brushes against the commutator. Such aninitial tension ofthe leaf springs is absolutely. required in order to attain the highestpossible contact pressure and thus the lowest possible contactresistance between the brushes and the commutator.

Prior to this invention, this initial tension of the leaf springs wasattained by bending them by means of tweezers. Such an adjustment of theinitial tension is, however, very complicated and inaccurate andrequires considerable time as well as great skill and experience.

It is an object of the present invention to provide a brush holder ofthe above-mentioned type which is designed and improved so as to permitthe initial tension of the leaf springs to be carried out very quicklyand accurately and in a very simple manner.

According to the present invention this object is attained 'by providinga setscrew for each leaf spring so that by the simple adjustment of thesetscrews by means of a screw driver, the leaf springs may be given veryeasily and quickly the exact initial tension as required.

In the conventional brush holders the leaf springs are usually insertedinto recesses and are held in this position by a cover which is thenconnected to the brush holder.

According to a preferred feature of the invention, however, the brushholder is provided with groove-like recesses which extend substantiallyvertical to the leaf springs and the walls of which are provided withpartial screw threads. A setscrew is then inserted into this recess fromthe open side thereof and is secured in its posit-ion within the recessby the application of the cover. The front ends of these setscrews thenengages directly upon the pivotable leaf springs, and when the setscrewsare turned in one direction or the other, the initial tension of theleaf springs is increased or reduced.

Another important feature of the invention resides in the simplicity ofmanufacture and installation of the :brush holder. This is attained bymaking the brush holder of an elastic material, for example, a suitableplastic, and by simply pressing the setscrews into the plain untappedrecesses so that the screw threads of the setscrews will be impressedinto the walls of the recesses and thus form corresponding screw threadstherein. The brush holder may thus be made, for example, of athermoplastic by means of a simple mold, and the recesses do not have tobe provided with any screw threads for receiving the setscrews sincethese screw threads are formed in the recesses automatically by thesetscrews themselves when they are pressed into the recesses from theiropen sides which are subsequently closed-by the cover which then retainsthe setscrews tightly within the impressed screw threads of therecesses. If the setscrews are made of a suflicient length as to projectfrom the outer ends of the recesses, they may then be easily adjusted bya screw driver, preferably by one which has a projecting socket whichengages over the projecting part of the setscrew and thus prevents thescrew driver from slipping out of the slot of the screw. According toanother embodiment of the invention, the

3,254,249 Patented May 31, 1966 setscrews may, of course, also be in theform of grub screws, the outer ends of which are sunk into the outerends of the recesses which are then preferably conically enlarged to theoutside to permit the screw driver to be easily inserted.

The feature of the invention of pressing setscrews into plain untappedgrooves so as to form corresponding screw threads therein and then tohold the setscrew therein by a cover is not limited to brush holders,but may also be applied to other devices or apparatus.

The features and advantages of the present invention will become moreclearly apparent from the following detailed description thereof whichis to be read with reference to the accompanying drawings, in which-FIGURE 1 shows a front view of a brush holder according to the inventionwith brushes and setscrews inserted therein;

FIGURE 2 shows a top view of the brush holder according to FIGURE 1 withthe cover applied thereon;

FIGURE 3 shows a top view of the cover according to FIGURE 2;

FIGURE 4 shows a cross section which is taken along line IVIV of FIGURE2; while 1 FIGURE 5 shows a side view which is taken from the left sideof FIGURE 2.

The brush holder 1 according to the invention may consist, for example,of a thermoplastic material and be made by injection molding. It isprovided with slots 2 into which leaf springs 3 are inserted, the lowerend of each of which carries a member 4, for example, a brush pad of anelectrically conductive material which engages upon the commutator 5.Each leaf spring 3 has a lateral extension 6 which engages into a slot 7so that the leaf springs are prevented from shifting in the axialdirection.

The brush holder 1 is further provided with guide grooves 8 into whichsetscrews 9 are impressed and are held in this position by a cover 10which may consist of the same material as the brush holder 1 and may besecured to the brush holder 1 by means of screws or rivets. Theguidegrooves 8 originally do not contain any screw threads, but setscrews 9are impressed into them from their open sides in such a manner that thecorresponding threads are formed therein automatically. When setscrews9, the front ends 9' of which engage upon the leaf springs 3, are turnedin one direction or the other, the tension of leaf springs 3 will beincreased or reduced.

Since setscrews 9 are pressed by force into guide grooves 8 and are heldtherein by the cover 10, these setscrews will be securely clamped inguide grooves 8 in any position to which they are adjusted. Thus,'anyunintentional adjustment of these setscrews during the operation of theelectric motor is completely prevented and, having once been made, anyadjustment of the tension of leaf springs 3 will always be maintained.

Although my invention has been illustrated and described with referenceto the preferred embodiment there of, I wish to have it understood thatit is in no way limited to the details of such embodiment, but iscapable of numerous modifications withinthe scope of the appendedclaims.

Having thus fully disclosed my invention, what I claim is:

1. A commutator brush holder for an electric motor comprising a brushholding member having spring receiving recesses therein and groovelikerecesses extending substantially at right angles to said springreceiving recesses, leaf springs having first ends inserted in thespring receiving recesses from one side of the brush holding member,said leaf springs having second projecting ends with brushes thereonadapted to be pressed by said leaf springs against the commutator ofsaid motor, set screw means adapted to be inserted from said side intothe groovelike recesses for acting on the leaf springs intermediate saidfirst and second ends thereof to adjust the initial stress.

elastic insulating material, said brush holding member' having springreceiving recesses therein and groovelike recesses extendingsubstantially at right angles to said spring receiving recesses, saidgroovelike recesses being initially unthreaded, said setscrews adaptedto be pressed from one side of the brush holding member into saidgroovelike recesses so that the screw threads thereof will then bepressed into said unthreaded walls which are thus provided withcorresponding screw threads, leaf springs adapted to be inserted intosaid spring receiving recesses from said side, and a cover adapted to besecured to said side for retaining said leaf spring and said setscrewsin said recesses.

3. A commutator brush holder as defined in claim 1, in which the outerends of said groovelike recesses are conically enlarged toward theoutside and said setscrews consist of grub screws having slotted endssunk into said groovelike recesses from said outer ends.

References Cited by the Examiner FOREIGN PATENTS 16,567 1884 GreatBritain.

MILTON O. HIRSHFIELD, Primary Examiner.

ORIS L. RADER, Examiner.

C. W. DAWSON, Assistant Examiner.

1. A COMMUTATOR BRUSH HOLDER FOR AN ELECTRIC MOTOR COMPRISING A BRUSHHOLDING MEMBER HAVING SPRING RECEIVING RECESSES THEREIN AND GROOVELIKERECESSES EXTENDING SUBSTANTIALLY AT RIGHT ANGLES TO SAID SPRINGRECEIVING RECESSES, LEAF SPRINGS HAVING FIRST ENDS INSERTED IN THESPRING RECEIVING RECESSES FROM ONE SIDE OF THE BRUSH HOLDING MEMBER,SAID LEAF SPRINGS HAVING SECOND PROJECTING ENDS WITH BRUSHES THEREONADAPTED TO BE PRESSED BY SAID LEAF SPRINGS AGAINST THE COMMUTATOR OFSAID MOTOR, SET SCREW MEANS ADAPTED TO BE INSERTED FROM SAID SIDE INTOTHE GROOVELIKE RECESSES FOR ACTING ON THE LEAF SPRINGS INTERMEDIATE SAIDFIRST AND SECOND ENDS THEREOF TO ADJUST THE INTIAL STRESS THEREOF, AND ACOVER ADAPTED TO BE SECURED TO SAID SIDE FOR RETAINING SAID LEAF SPRINGSAND SAID SETSCREWS IN SAID RECESSES.